Muscle tissue contains approximately 75% of water and 20% of protein consisting of sarcoplasmic, myofibrillar, and connective-tissue proteins. During heating, the thermal denaturation of the meat proteins occurs. According to differential scanning calorimetry measurements, a-actinin denatures at 50 °C; myosin and actomyosin between 54 and 58 °C; sarcoplasmic proteins between 65 and 67 °C; actin between 80 and 83 °C; tropomyosin and troponin at above 80 °C; and titin at 75.6 °C (in beef) or 78.4 °C (in pork). Generally, during heating the globular (sarcoplasmic) proteins expand and fibrous (myofibrillar) proteins contract. The intramuscular collagen fibers shrink in the range of temperature 53–65 °C and gelatinize on further heating (70–80 °C). The structural changes in the meat proteins on heating lead to alterations in the eating quality of meat."
They should put that in an Outback Steakhouse commercial, it really sets my mouth to waterin!
Which I suppose makes me a leaky ugly bag of mostly water.